1. Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
2. Faculty of Medicine and Health Sciences, University Malaysia Sabah, Kota Kinabalu 88400, Malaysia
3. Division of Infectious Diseases, Department of Medicine, National University Health System, Singapore 119228, Singapore
4. Division of Infectious Diseases, Department of Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia
5. Department of Radiation Oncology, National University Cancer Institute, Singapore 119074, Singapore